Abstract : The amount of pyridostigmine which can be tolerated without severe side effects appears to be related to the degree of impairment of neuromuscular transmission. Myasthenic patients may routinely ingest as much as several grams of pyridostigmine per day. Surgical patients whose normal nerve transmission is blocked by muscle relaxants can tolerate intravenous doses equivalent to oral doses of 300-600 mg. The studies in military personnel indicate that doses of 30 mg at eight hour intervals are tolerated by persons with normal neuromuscular transmission. Based on the results of the military studies and the general Lack of side effects other than overdose symptoms cited in the medical Literature after thirty years of extensive use, it can be concluded that administration of pyridostigmine to normal subjects is probably safe at Low doses, i.e. 30 mg at 8 hour intervals. Although normal subjects may tolerate somewhat higher doses without excessive side effects and without diminished task performance, there are no published reports of such studies.